Testing math functions

Hi - I've writing a few tests for the math extension and have a question about floating point precision. Here's a small example: --TEST-- Test return type and value for expected input sin() --INI-- precision = 14 --FILE-- <?php $threesixty = pi() * 2.0; echo "sin 360 = "; var_dump(sin($threesixty)); ?> --EXPECT-- sin 360 = float(-2.4492127076448E-16) Is it right to test for an exact number in this way? I was slightly suprised that I got the same number from Windows and Linux (maybe I shouldn't be). If not, I could write the test above to check that sin 360 is zero plus/minus some small number - but how small? Zoe Slattery IBM